The acronym “KERS” stands for Kinetic Energy Recovery System. The KERS device recovers the kinetic energy that is present in the waste heat created by a car's braking process. It stores that energy and converts it into electrical or mechanical power that can be called upon to boost acceleration.
There are two types of KERS system; battery (electrical) and flywheel (mechanical). Electrical systems use a motor-generator incorporated in the car's transmission which converts mechanical energy into electrical energy and vice versa. Once the energy has been harnessed, it is stored in a bank of lithium ion batteries and released when required.
The KERS system has been used in Formula One racing cars. The rules of Formula One allowed the KERS system to deliver a maximum of 60 kW extra power (approximately 80 bhp), while the storage capacity is limited to 400 kilojoules. The extra 60 kW of power (equivalent to ten percent of peak engine power) is available for anything up to 6.67 s per lap, and can be released at the press of a boost button either all in one go, or at different points around the racing track. Consequently, the KERS system can provide lap time improvements in the range of from about 0.1 seconds to 0.4 seconds.
Advantageously, the KERS system promotes the development of environmentally friendly and road car-relevant technologies in Formula One racing, and helps the driver with overtaking. A chasing driver can use his boost button to help him pass the car in front, while a leading driver can use his boost button to escape the car behind.
The quest for vehicle fuel efficiency in road cars has lead to the development of hybrid vehicles by a number of automobile companies. As used herein, the term “hybrid vehicle” refers to a vehicle having two means of propulsion, for example, (1) a combustion engine either gasoline or diesel fuelled and (2) an electric motor receiving power from on-board batteries which are charged by engine (1) or by regenerative braking. Using the KERs system in road cars would help to reduce their fuel consumption.
The typical method of cooling the electric battery in the KERS system is by air cooling. However, air cooling is not always sufficient, and liquids such as water are not considered suitable. It has now surprisingly been found by the present inventors that lubricating compositions comprising certain components and having certain physical properties provide excellent cooling and/or insulating benefits when used in the electric battery or electric motor of a KERS system. It has also been found that said lubricating compositions can provide excellent cooling and/or insulating benefits in the electric battery or electric motor of a hybrid vehicle.